1. Field of the Invention
This invention relates to a method of making a composite member by forming a base material constituted by an aluminum alloy integrally with a composite member constituted by an aluminum composite material corresponding to a desired target function.
2. Description of the Prior Art
In recent years, aluminum alloys have been increasingly employed for mechanical structures such as cylinder heads of reciprocating engines for decreasing weight. In the mechanical structure fabricated of an aluminum alloy, it is often required to impart a desired target function to specific parts thereof in order, for example, to improve the resistance to wear or resistance to thermal fatigue.
To meet this requirements, the practice has been to coat a predetermined surface of a base material formed of an aluminum alloy with a metal corresponding to the target function, for example, Mo or 0.8C-Fe for improving the resistance to wear, by gas sputtering. It has also been proposed, for example, in Japanese Unexamined Patent Publication No. 56(1981)-77374, to form an aluminum-aluminum nitride mixture layer on the surface of an aluminum material by a plasma spray method, and to form a covering layer by firing. As the means for imparting the target function to the base material, the brazing method or the hot pressing method may also be used. However, in the case where the area of the surface to which the target function has to be imparted is large or the shape of the base material is complicated, air bubbles arise at the bonding section when brazing is conducted, and the bonding strength becomes low. Further, when the shape of the base material is complicated, the hot pressing method cannot be used.
Particularly, in recent years, mechanical structures are mostly formed into a complicated shape by casting, and the area of the surface to which the target function has to be imparted is made large. Therefore, in many cases, the coating method is employed.
However, in the conventional coating method based on sputtering or plasma spraying, adhesion of the metal for imparting the target function to the base material is low. Therefore, the coating layer readily peels off, and the durability is low. Particularly, in the case where high resistance to wear is required as the target function for slideways or the like, the peeling-off of the coating layer is readily caused by repetitive sliding.